It is well known to employ an array of elements which are individually not very directional to create an antenna which is highly directional. If the array is linear, the antenna beam is fan-shaped. If the array is two-dimensional, the beam is a pencil beam. The narrowness of the beam and hence the antenna gain are influenced in particular by the number of elements in the array.
Although not limited to any particular application, the invention has been conceived in the context of a particular problem, namely the provision of a receiving antenna for a DBS (direct broadcasting by satellite) receiver. Attention is currently concentrated mainly upon parabolic dish antennae for this purpose. Such antennae are large in all three dimensions and of inelegant appearance: their proliferation in residential areas will seriously degrade the environment. There exists a need for an antenna which does not suffer from these defects and which is also of a more inherently robust construction than a dish antenna with its struts supporting a feed-horn.
An array antenna offers the advantage of a robust construction but for DBS usage it is necessary to achieve a very high gain and make suitable provision for aiming the antenna at the desired geostationary satellite. If this were to be done purely by physical positioning (as with a dish antenna), the advantage of a flat, unobtrusive construction is largely lost. What is required is to be able to mount the antenna flat on a suitable wall or possibly roof surface. Moreover, the superficial dimensions of the antenna must be within reasonable bounds if it is to be possible to find suitable mounting areas, say no more than around 1m on the side or diameter. Nevertheless, it must be possible to pack in a large number of elements to get adequate gain which demands that the elements themselves be compact.